A hem on a T-shirt, made with a coverlock machine

The finished backside of a coverlocked seam

My coverlock machine, a Janome Coverpro 1000 CPX

A coverlock is a type of sewing machine that is dedicated to do a coverlock stitch, or coverlock seam.

A coverlock seam is used for hemming knit garments. It finishes the folded back fabric so it can’t ravel and the resulting stitch can stretch along with the fabric.

Coverlocks can be dedicated machines, or they can be integrated in an overlock/serger.